The global redirect feature lets you redirect users from the End-User Dashboard if they sign in to your org without app context. It’s useful when users reset their passwords or if Okta can’t determine which app they’re trying to access.
In Classic Engine, you configure the redirect by entering a custom URL in the Default App for Sign-In Widget section of your customization settings. In Identity Engine, you select an app in your org to serve as the redirect.
If you have a custom URL when you upgrade, Okta creates a bookmark app called OIE Default Redirect App and assigns your custom URL to it. The bookmark app provides the same experience as your custom URL in Classic Engine. You can choose a different app if you don't want to use the bookmark app. If you select an OIDC app, be sure to also set an initiate_login_URI.
The timing of the redirect is the only difference for users. In Classic Engine, the redirect occurs after they authenticate. In Identity Engine, the redirect occurs before they authenticate (unless you chose an OIDC app, in which case the redirect occurs after user authentication).